Intraoperative indocyanine green video-angiography: spinal dural arteriovenous fistula

Spinal Dorsal Intradural Arteriovenous Fistulas: Natural History, Imaging, and Management

In this review, we describe the pathophysiology, diagnosis, and treatment of spinal dorsal intradural arteriovenous fistulas (DI-AVFs), focusing on novel research areas. DI-AVFs compose the most common subgroup of spinal arteriovenous lesions and most commonly involve the thoracic spine, followed by lumbar and sacral segments. The pathogenesis underlying DI-AVFs is an area of emerging understanding, thought to be attributable to venous congestion and hypertension that precipitate ascending myelopathy. Patients with DI-AVFs typically present with motor, sensory, or urinary dysfunction, although a wide swath of other less common symptoms has been reported. DI-AVFs can be subdivided by spinal region, which in turn is associated with 4 distinct clinical phenotypes: craniocervical junction (CCJ), subaxial cervical, thoracic, and lumbosacral. Patients with CCJ and lumbosacral DI-AVFs have particularly interesting presentations and treatment considerations. High-value diagnostic findings on MRI include flow voids, missing-piece sign, and T2-weighted intramedullary hyperintensity. However, digital subtraction angiography is the gold standard for diagnosis and localization of DI-AVFs and for definitive treatment planning. Surgical disconnection of DI-AVFs is almost universally curative and frontline treatment, especially for CCJ and lumbosacral DI-AVFs. Endovascular techniques evolve in promising ways, such as improved visualization, distal access, and liquid embolic techniques. The pathophysiology of DI-AVFs is better understood using newly identified radiologic diagnostic markers. Despite new techniques and devices introduced in the endovascular field, surgery remains the gold-standard treatment for DI-AVFs.

Review of Avoidance of Complications in Cerebral Aneurysm Surgery: The Fujita Experience

Avoidance of complications during cerebral aneurysm surgery marks the future outcome in the patient. Various modalities such as adequate opening of the Sylvian fissure, motor-evoked potential, endoscope-assisted microsurgery, indocyanine green dye, and dual image video angiography are available to reduce these complications during surgery, either by prevention of injury to the small perforators or the parent artery. We present our experience at the Fujita Health University Banbuntane Hospital, Japan, of the cerebral aneurysm surgery along with the use of these modalities in our patients from September 2014 to December 2016 along with a brief review of the various techniques for avoidance of complications.

Application of indocyanine green video angiography in vascular neurosurgery

Indocyanine green video angiography (ICG-VA) is a non-invasive, easy to use and very useful tool for various neurosurgical procedures. The first application was in neurovascular surgery, because it was born as an intravascular tracer for vessels visualization; this has been really useful in aneurysms, atero-venous malformations (AVMs) and dural fistulas surgery where identification, obliteration or patency of vessels is essential. Introduced in vascular neurosurgery since 2003, ICG-VA applications have broadened over time, both in vascular and in other neurosurgical fields. In 2003 Raabe et al. have been the first to describe the use of ICG-VA for intraoperative assessment of cerebral vascular flow, enabling visualization of vessel patency and aneurysm occlusion during aneurysm surgery. ICG-VA applications in vascular neurosurgery have significantly increased over time including complex aneurysms, bypass, atero-venous malformations (AVM) artero-venous fistulas (AVF), evaluation of cortical perfusion. The procedure can be easily repeated after 5-10 minutes. Adverse reactions are comparable to those of other types of contrast media, with frequencies of 0.05% (hypotension, arrhythmia, or, more rarely, anaphylactic shock) to 0.2% (nausea, pruritus, syncope, or skin eruptions. The aim of the present study was to systematically analyze ICG-VA applications in vascular neurosurgery, highlighting the reported advantages and disadvantages, and discussing future perspectives.

Efficacy of Intraarterial Fluorescence Video Angiography in Surgery for Dural and Perimedullary Arteriovenous Fistula at Craniocervical Junction

OBJECTIVE

Confirming the exact location of a fistula and the origins of draining veins during surgery for dural and perimedullary arteriovenous fistulas (AVFs) is crucial but sometimes inadequately performed, which can result in incomplete elimination of the lesion. Intraoperative digital subtraction angiography (DSA) is the gold standard for confirming the hemodynamics of an AVF; however, it cannot reveal the location of an AVF in the operative field. In this study, the efficacy of intraoperative intraarterial fluorescence video angiography during surgery for craniocervical junction dural and perimedullary AVFs was investigated.

METHODS

We repeatedly employed this technology to evaluate its usefulness in revealing the flow dynamics and anatomy of AVFs and to confirm complete elimination of the fistula.

RESULTS

Seven AVFs were included in this study. Their locations were C1 in 5 cases and C2 in 2 cases. Intraarterial fluorescence video angiography precisely revealed the locations of 3 dural AVFs, 1 perimedullary AVF, and 3 co-occurring dural and perimedullary AVFs. Frame-by-frame review of the fluorescence video angiography clearly demonstrated that fluorescence appeared earlier in the perimedullary AVF than in the draining vein through the dural AVF after intraarterial injection in all 3 co-occurring cases. Complete elimination of the AVF was also confirmed in all cases by fluorescence video angiography, as well as intraoperative and follow-up DSA.

CONCLUSIONS

Intraarterial fluorescence video angiography, particularly frame-by-frame review, enables surgeons to distinguish the flow dynamics of AVFs and contributes to the planning of effective surgical strategies for optimal results.

Use of a New Indocyanine Green Pooling Technique for Improved Visualization of Spinal Dural AV Fistula: A Single-Center Case Series

BACKGROUND

Intraoperative indocyanine green video angiography (ICG-VAG) is a useful tool in cerebral vascular surgery. In spinal procedures such as dural arteriovenous (AV) fistula, use of ICG-VAG is limited due to lower perfusion pressure. Therefore, we developed a new pooling technique with adapted workflow to improve intraoperative visualization.

METHODS

Patients operated on spinal dural AV fistulas using ICG-VAG were prospectively included. A new workflow for ICG-VAG was applied: 1) temporary clip placement at the suspected fistula point, 2) ICG administration during 100% oxygenation, 3) ICG pooling proximal of temporary clip, 4) clip removal/observation of vascular filling. Case records, clinical data, magnetic resonance imaging, digital subtraction angiography (DSA), and clinical outcome were analyzed retrospectively.

RESULTS

A total of 11 patients (median age 68 years, average course of disease 15 months) were included. Optimized, inverted workflow resulted in considerable pooling of ICG in the supplying feeder of the AV fistula in all cases. Complete obliteration was confirmed in 10 of 11 patients by postoperative DSA. However, 1 patient had an additional, preoperative radiologically undetected small feeder that enlarged until postoperative DSA and made successful reoperation necessary. After the median follow-up of 33.2 months, the Aminoff-Logue scale was decreased in all patients, and the McCormick score (modified Rankin score) was improved in 9 (8) patients and remained stable in 2 (3) patients.

CONCLUSIONS

Procedure modification in terms of ICG pooling enabled us to detect more easily the pathologic vascular architecture. ICG-VAG is a useful adjunct in the surgical treatment of spinal dural AV fistula because it is a real-time, noninvasive, and radiation-free technique with adequate image resolution.

Role of intraoperative indocyanine green video-angiography to identify small, posterior fossa arteriovenous malformations mimicking cavernous angiomas. Technical report and review of the literature on common features of these cerebral vascular malformations

OBJECTIVE

To illustrate the usefulness of intraoperative indocyanine green videoangiography (ICG-VA) to identify the nidus and feeders of a small cerebellar AVM resembling a cavernous hemangioma. To review the unique features regarding the overlay between these two vascular malformations and to highlight the importance to identify with ICG-VA, and treat accordingly, the arterial and venous vessels of the AVM.

METHODS

A 36-year old man presented with bilateral cerebellar hemorrhage. MRI was equivocal in showing an underlying vascular malformation but angiography demonstrated a small, Spetzler-Martin grade I AVM. Surgical resection of the AVM with the aid of intraoperative ICG-VA was performed. After hematoma evacuation, pre-resection ICG-VA did not reveal tortuous arterial and venous vessels in keeping with a typical AVM but rather an unusual blackberry-like image resembling a cavernous hemangioma, with tiny surrounding vessels. Such intraoperative appearance, which could also be the consequence of a "leakage" of fluorescent dye from the nidal pathological vessels, with absent blood-brain barrier, into the surrounding parenchymal pathological capillary network, is important to be recognized as an unusual AVM appearance.

RESULTS

Post-resection ICG-VA confirmed the AVM removal, as also shown by postoperative and 3-month follow-up DSAs.

CONCLUSIONS

Despite technical limitations associated with ICG-VA in post-hemorrhage AVMs, this case together with the intraoperative video, demonstrates the useful role of ICG-VA in identifying small AVMs with peculiar features.

Indocyanine green videoangiography methodological variations: review

Indocyanine green videoangiography (ICGVA) procedures have become widespread within the spectrum of microsurgical techniques for neurovascular pathologies. We have conducted a review to identify and assess the impact of all of the methodological variations of conventional ICGVA applied in the field of neurovascular pathology that have been published to date in the English literature. A total of 18 studies were included in this review, identifying four primary methodological variants compared to conventional ICGVA: techniques based on the transient occlusion, intra-arterial ICG administration via catheters, use of endoscope system with a filter to collect florescence of ICG, and quantitative fluorescence analysis. These variants offer some possibilities for resolving the limitations of the conventional technique (first, the vascular structure to be analyzed must be exposed and second, vascular filling with ICG follows an additive pattern) and allow qualitatively superior information to be obtained during surgery. Advantages and disadvantages of each procedure are discussed. More case studies with a greater number of patients are needed to compare the different procedures with their gold standard, in order to establish these results consistently.

Uses and limitations of indocyanine green videoangiography for flow analysis in arteriovenous malformation surgery

Intra-operative indocyanine green (ICG) videoangiography is a useful addition to cerebrovascular neurosurgery. ICG videoangiography is useful in different phases of arteriovenous malformation (AVM) surgery. Additionally, it can be used to perform semi-quantitative flow analysis. We reviewed our initial assessment of 24 patients who underwent ICG videoangiography during AVM surgery to assess the utility and limitations of the technique as well as to demonstrate semi-quantitative flow analysis, a new capability of ICG videoangiography. Over the course of 3 years, we performed 49 ICG videoangiographies in 24 patients with AVM. In 85% of the pre-resection videos, ICG was useful in localising the arterial feeders, the draining veins and the nidus. Intra-resection ICG videos were recorded for eight of the 23 patients (the ICG from one patient was missing). Post-resection ICG videos were recorded for 14 out of the 23 patients, which were useful in confirming no evidence of nidus in the exposed resection cavity and an absence of flow in the main draining vein. Semi-quantitative flow analysis was performed in eight patients with superficial AVM. The average T(½) peak intensities (time to 50% of peak intensity) were 32 s, 33.5 s, and 35.6 s for the arterial feeder, the draining vein and normal cortex, respectively. The arteriovenous T(½) peak time was 1.5 s, and the arteriocortex T(½) peak time was 3.6 s. The T(½) peak fluorescence rates were 84 average intensity of fluorescence (AI)/s, 62.9 AI/s and 28.7 AI/s, for the arterial feeder, the draining vein and normal cortex, respectively. Only one patient of 23 (4.3%) showed residual AVM on post-operative digital subtraction angiography or CT angiography despite negative intra-operative ICG. ICG videoangiography is a useful addition to AVM surgery, but it has some limitations. Flow analysis is a new capability that allows for semi-quantitative AVM perfusion analysis.

Intraoperative Near-infrared Fluorescence Imaging with Novel Indocyanine Green-Loaded Nanocarrier for Spinal Metastasis: A Preliminary Animal Study

Marginal resection during resection of a spinal metastasis is frequently difficult because of the presence of important tissues such as the aorta, vena cava, and dura mater, including the spinal cord adjacent to the vertebral body. Thus, there is an urgent need for novel intraoperative imaging modalities with the ability to clearly identify bone metastasis. We have proposed a novel nanocarrier loaded with indocyanine green (ICG) (ICG-lactosome) with tumor selectivity attributable to its enhanced permeation and retention (EPR) effect. We studied its feasibility in intraoperative near-infrared (NIR) fluorescence diagnosis with ICG-lactosome for imaging spinal metastasis. A rat model of subcutaneous mammary tumor and a rat model of spinal metastasis of breast cancer were used. Fluorescence emitted by the subcutaneous tumors and the spinal metastasis were clearly detected for at least 24 h. Moreover, imaging of the dissected spine revealed clear fluorescence emitted by the metastatic lesion in the L6 vertebra while the normal bone lacked fluorescence. This study was the first report on NIR fluorescence imaging of spinal metastasis in vivo. NIR fluorescence imaging with ICG-lactosome could be an effective intraoperative imaging modality for detecting spinal metastasis.